The purpose of this research is to delineate barriers, pathways and transport mechanisms within the normal and altered cochlea, espeically within the stria vascularis, utilizing electron microscopy and histochemical labeling. Transport will be altered by changing vascular osmolarity with osmotic diuretics and plasma expanders such as mannitol, dextran, glycerol and loop-inhibiting diuretics such as ethacrynic acid and bumetanide and histamine, histamine site receptor stimulators and antihistamines. The alterations will be investigated with light and electron microscopy utilizing exogenous protein tracers such as horseradish peroxidase, and labelled mannitol and dextran. Adenylate cyclase, cyclic AMP, and phosphodiesterase (PPDE) activity will be investigated by electron microscopic localization techniques in the normal and the altered states created in the above pathologies. Our immediate and most prominent objective is to further understand the mechanism involved in the creation of stria edema caused by different types of diuretics, kidney pathology and acoustic trauma. The ultimate objective is to add further understanding to the function of the normal membranous labyrinth, particularly mechanisms leading to endolymphatic hydrops and sudden deafness. The studies will be done on the chinchilla and guinea pig.